To understand the mechanisms that contribute to renal disease, it is first necessary to understand the normal physiology of renal function. Thus in the following chapters in this section of the book, various aspects of renal function are considered.
Functional Anatomy of the Kidneys
Structure and function are closely linked in the kidneys. Consequently an appreciation of the gross anatomical and histological features of the kidneys is a prerequisite for understanding their functions.
The kidneys are paired organs that lie on the posterior wall of the abdomen behind the peritoneum on either side of the vertebral column. In an adult human, each kidney weighs between 115 and 170 g and is approximately 11 cm long, 6 cm wide, and 3 cm thick.
The gross anatomical features of the human kidney are illustrated in
Fig. 33.1 . The medial side of each kidney contains an indentation through which pass the renal artery and vein, nerves, and pelvis. If a kidney were cut in half, two regions would be evident: an outer region called the cortex and an inner region called the medulla. The cortex and medulla are composed of nephrons (the functional units of the kidney), blood vessels, lymphatics, and nerves. The
Kidney disease is a major health problem worldwide. In the United States alone:
CKD affects over 23 million patients and accounts for more than 90,000 deaths annually.
Kidney diseases represent the ninth leading cause of death.
The health care cost for CKD in Medicare patients alone exceeds $44 billion per year.
Each year, kidney disease is diagnosed in over 3 million new patients.
Over 500,000 people are treated for ESRD every year.
Approximately 275,000 patients with ESRD are maintained on either hemodialysis or peritoneal dialysis.
Diabetes and hypertension are the leading causes of ESRD.
ESRD secondary to diabetes is increasing at an annual rate of more than 11% per year.
More than 17,000 kidney transplants are performed each year. Unfortunately, in excess of 100,000 patients are awaiting kidney transplants.